Crack Evolution and Damage Mechanisms of Double‐Flawed Sandstone Monitored Under DIC and AE: The Influence of Rock Bridge Angle

ABSTRACT The synergistic mechanism between crack network evolution and energy release in deep coal mine roof sandstone is a critical factor triggering rock burst disasters. This study combined acoustic emission (AE) monitoring with digital image correlation (DIC) technology to conduct uniaxial compression tests on double‐flawed sandstone, systematically analyzing how rock bridge dip angle regulates crack propagation paths and damage evolution. A mechanical criterion for mixed‐mode crack propagation was developed based on stress intensity factor theory, optimizing traditional crack classification standards. Results show that as rock bridge dip angle increases, crack penetration length shortens, energy dissipation channels decrease, and AE energy accumulation intensifies. Under low rock bridge angles, tensile stress drives crack initiation with predominantly mixed I/II propagation modes, whereas at high angles, cracks initiate via shear slip, dominated by mixed III modes. The regulatory mechanism of rock bridge dip angle on crack network configuration and energy release paths is revealed, providing a theoretical basis for achieving directional energy release in roof rock through active optimization of rock bridge angles.